In the field of integrated circuit devices, and in particular in the field of application processor integrated circuit devices, modern integrated circuit devices are required to provide increasingly high performance whilst bring also required to fulfil increasingly stringent power consumption and thermal energy dissipation requirements.
In order to optimise power consumption and performance, it is known to use on-chip power management techniques that regulate voltage and frequency settings within the respective integrated circuit device depending upon current performance/power requirements. Such power management techniques include power gating and dynamic voltage frequency scaling (DVFS), etc. In order to enable such power management, voltage regulators are required. However, a problem arising from the use of such voltage regulators is that their use physically ‘on-chip’ often results in an increased thermal power budget requirement for power dissipation of the integrated circuit device package for high frequency devices. This results in an increase in cost and (significantly) size of the integrated circuit package. The power dissipated by a regulator may be approximated, as shown in Equation 1 below:Pdis≈Ireg*(Vin−Vout)  [Eq. 1]
A known solution to this problem is to provide a simple regulator, located external to the integrated circuit device to act as a pre-regulator, and then to provide a more sophisticated on-chip regulator to provide the final required voltage. In this manner, the requirements for the on-chip regulator may be reduced, thereby enabling tighter thermal power budgets. However, such a solution still requires careful control of the on-chip regulator in order to meet the tight thermal power budgets. This typically requires the on-chip regulator to be kept in a ‘bypass’ mode for the highest frequencies, in order to minimize its power consumption, with the external regulator providing the voltage regulation at such high frequencies.
Referring first to FIGS. 1 and 2, a known thermal budget for the integrated circuit (IC) device is defined by a thermal limit 110 up to which the packaging for the IC device is capable of effectively dissipating thermal power. A significant proportion of the thermal budget for the IC device is taken up by dynamic and leakage power consumed by SoC (System on Chip) internal modules, etc., as illustrated at 120. The remaining available thermal power budget, illustrated at 130 in FIG. 1, is thus available for the thermal power dissipation of internal voltage regulators and the like. Typically, in order to keep packaging costs, etc., to a minimum, the remaining available power budget is typically very limited. If internal voltage regulation is performed at high operating frequencies, it is often the case that the required thermal power budget for the internal voltage regulators will exceed the available power budget. Thus, the overall power budget for the IC device may exceed the thermal limit 110 of the IC packaging, as illustrated in FIG. 2. Thus, in order to avoid the IC device overheating during high frequency operation, internal voltage regulators are configured to a bypass mode, with external voltage regulators performing the required voltage regulation.
However, a problem with using external voltage regulators is that, in order to avoid high costs, simple voltage regulators that are typically only capable of providing coarse regulation used. As a result, the ability to achieve a maximum junction voltage using such external voltage regulators is extremely difficult, which limits the achievable operating frequency of the IC device. Thus, it is desirable to minimise the need for relying on such external voltage regulators.